The present invention relates generally to the field of energy usage in processors and in particular, to energy usage estimation of program code executable by very long instruction word (VLIW) processors.
Digital signal processors (DSPs), such as very long instruction word (VLIW) processors, are widely used in hand-held electronic devices such as mobile phones, personal digital assistants (PDAs), and digital cameras. Low power is an important criterion for the hand-held devices, which have limited power reserves. The energy consumed by software executed by a processor can be used to determine the total power and energy requirements of the processor, and therefore, to predict the battery life of a hand-held device using the processor. Software energy estimation can also be used as a starting point for software optimization techniques for reducing power consumption of the processor.
There are several known approaches for estimating software energy consumption. These include gate-level, micro-architectural level, and instruction level approaches. The instruction level approach is very useful from application software power profiling perspective. In this approach, a base energy consumption is associated with each instruction of the software. In addition, an inter-instruction energy consumption is associated with each instruction to account for the energy cost associated with change from previous instructions to present instruction. However, some of the methods that use the instruction level approach associate a constant energy cost for the inter-instruction effect.
Other methods of modeling inter-instruction energy cost involve clustering of similar instructions into different groups. A look up table that includes energy values for change in the instructions from one group to another group is then used to estimate the energy of the software. However, these approaches work well for simple processors such as single issue processors. Further, considerable memory space is required to store the look-up tables.
It is an object of the present invention to provide a method of accurately estimating processor energy usage especially for VLIW processors. It is also an object of the present invention to provide such a method without requiring considerable memory space.